features: add runtime attestation page

We've supported runtime attestation from the workload for a few releases.
Let's add a feature page describing how to use it.

Signed-off-by: Tobin Feldman-Fitzthum <tfeldmanfitz@nvidia.com>

Author: fitzthum

content/en/docs/features/runtime-attestation.md

@@ -0,0 +1,124 @@
+---
+title: Runtime Attestation
+date: 2025-01-08
+description: Measurement from workload at runtime
+categories:
+- feature 
+tags:
+- attestation 
+---
+Workloads can request runtime attestation of arbitrary data via a generic interface.
+Not all hardware platforms support runtime attestation, but those that do
+will fulfill the request.
+
+On these platforms, the Attestation Agent maintains an event log,
+which tracks attestation events. This log will be forwarded to Trustee
+via the KBS protocol and compared to the hardware evidence.
+
+### Enabling
+
+To enable this feature, set the following parameter in the guest kernel command line.
+```bash
+agent.guest_components_rest_api=all
+```
+{{% alert title="Warning" color="primary" %}}
+Note that this configuration will also allow the workload to fetch attestation
+reports at runtime. In some configurations this can be dangerous.
+See [attestation report](get-attestation) page for more information.
+{{% /alert %}}
+
+The Attestation Agent configuration must also have runtime attestation enabled.
+This can be set via Init-Data, with the `[eventlog_config]` section below.
+This configuration can also specify the measurement index that will be used.
+On platforms with limited indices, the index will be mapped to the available
+registers. For example, on TDX setting the measurement index to 17 will usually
+result in extending RTMR 3.
+
+```toml
+version = "0.1.0"
+algorithm = "sha384"
+[data]
+"aa.toml" = '''
+[token_configs]
+[token_configs.kbs]
+url = "http://<trustee-uri>"
+
+[eventlog_config]
+init_pcr = 17
+enable_eventlog = true
+'''
+
+"cdh.toml" = '''
+[kbc]
+name = "cc_kbc"
+url = "http://<trustee-uri>"
+'''
+```
+
+The above configurations can be added to a workload as annotations.
+See the [Init-Data](initdata) page for more information on using Init-Data.
+```yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx
+  labels:
+    app: nginx
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: nginx
+  template:
+    metadata:
+      labels:
+        app: nginx
+      annotations:
+        io.katacontainers.config.hypervisor.kernel_params: "agent.guest_components_rest_api=all"
+	io.katacontainers.config.hypervisor.cc_init_data: "H4sIAAAAAAAAA4WOwQ6DIBBE7/sVhos3xGpSa9IvMYQgUiEiGFz9/kLTHtpLjzO7M29OHXcbfHEvCKM1ZQSkm0O0aNbs7UY2XUtgmCRKDkRKimF1JN3KsoQBw6K9UME/7LzzH02XMXlHdLnJIG59VdWMXtqWMnpr+o51iQeDPrVHF+Z3joP1FsWmYsrVV9Bejk6Lz1cyMR4aMh+Imsz3omVUHLxcdYYqJZImfze8up7xdiRhCwEAAA=="
+    spec:
+      runtimeClassName: (...)
+      containers:
+      - name: nginx
+        (...)
+```
+### Runtime Attestation
+
+Once enabled, runtime attestation can be triggered via the rest API.
+```bash
+curl -X POST http://127.0.0.1:8006/aa/aael \
+     -H "Content-Type: application/json" \
+     -d '{"domain":"test","operation":"test","content":"test"}'
+```
+
+The `domain` and `operation` are context fields that will be included in the event log.
+
+You can check that the event log was updated by inspecting an attestation token.
+```bash
+curl http://127.0.0.1:8006/aa/token\?token_type\=kbs | jq -r '.token |split(".") | .[1] | @base64d | fromjson'
+```
+The event log may contain boot-time entries, but at the end you should see your entry.
+
+```json
+{
+   "details":{
+      "data":{
+         "content":"test",
+         "domain":"test",
+         "operation":"test"
+      },
+      "string":"test test test",
+      "unicode_name":"AAEL"
+   },
+   "digest_matches_event":true,
+   "digests":[
+      {
+         "alg":"SHA-384",
+         "digest":"1495be3eb2120e59facb8f92447d64f..."
+      }
+   ],
+   "event":"TEVBQREAAAB0ZXN0IHRlc3QgdGVzenp6dA==",
+   "index":4,
+   "type_name":"EV_EVENT_TAG"
+}
+```